it has to be the GT and a couple of small SMALL plecos, ie 3-6". even small plecos are poop factories.
you do realise that even with the GT being the smallest out of the options you gave us you may still have to upgrade should it get bigger than about 8-9". they have the potential to hit 12"+, a rarity but still possible. my midas is only about 8.5" and she is beginning to make my tank look small, its not as tall but it is wider than a 55.